MURINE HOXC-9 GENE CONTAINS A STRUCTURALLY AND FUNCTIONALLY CONSERVEDENHANCER

Reporter gene analysis of the Hoxc-9 genomic region in transgenic mice allowed us to identify a positional enhancer in the Hoxc-9 intron tha t drives expression in the posterior neural tube of midgestation mouse embryos in a Hoxc-9-related manner. Sequence comparison to the chicke n Choxc-9 intron revealed the existence of two highly conserved sequen ce elements (CSEs) in a similar spatial arrangement. These structural similarities in the mammalian and avian lineage are mirrored by conser ved function of the chicken Choxc-9 intron in transgenic mice. Deletio n analysis of the two introns suggests that full activity of both enha ncers depends on cooperation between the two CSEs located close to the respective 5' and 3' splice sites. Following the paradigm of phylogen etically conserved developmental control mechanisms, the Hoxc-9 intrag enic enhancer was tested in Drosophila. Our data show that the mouse H oxc-9 enhancer acts in a conserved fashion in transgenic flies, confer ring posteriorly restricted reporter gene expression to the developing central nervous system in third instar larvae. This finding indicates that the Hoxc-9 intragenic enhancer is involved in transcriptional re gulatory circuits conserved between vertebrates and arthropods. (C) 19 98 Wiley-Liss,Inc.